The invention relates to medical devices formed of multi-filar, cross-wound coils, and in particular to catheter-like devices so formed.
Medical devices consisting of elongated spring coils are employed widely as guidewires, e.g., for negotiating tortuous and narrow passageways of the body to a site to be treated and then serving as guides for catheters or other larger diameter devices advanced over the guidewires. In order to obtain maximum performance and patient safety, it is important that the guidewire be as small in diameter as possible, particularly in the tip region (but not so small as to create a danger of the tip breaking loose in the body); that the distal tip region be highly flexible to permit negotiation of difficult turns within the body; that the guidewire also be stiff enough axially to be advanced by pressure from the proximal end outside the body; and that the guidewire have good steerability or torque response, i.e., the tip to handle turn ratio should be as close to 1:1 as possible, without whipping. Most prior art guidewires offer or comprise of these desired features, e.g., trading tip flexibility for good torque response
Another use of spring coils is in catheter-like medical devices which require characteristics similar to those described above. An example of such a device is described in Tate U.S. Pat. No. 3,841,308 as having a spring coil covered with a polyfluoroethylene flexible coating or sheath for delivery of fluid to ports adjacent the distal end.